Multilayer capacitor and board having the same mounted thereon

ABSTRACT

A multilayer capacitor includes a capacitor body including dielectric layers and first and second internal electrodes, the capacitor body having first to sixth surfaces, the first internal electrode being exposed through the third, fifth, and sixth surfaces, and the second internal electrode being exposed through the fourth, fifth, and sixth surfaces, a first side portion and a second side portion, respectively disposed on the fifth surface and the sixth surface of the capacitor body, and a first external electrode and a second external electrode, respectively be connected to the first internal electrode and the second internal electrode. The first and second side portions comprise an acicular second phase including a glass comprising aluminum (Al) and silicon (Si), manganese (Mn), and phosphorus (P), and a volume of the second phase is 30% or more with respect to the entire first and second side portions.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 USC 119(a) of Korean Patent Application No. 10-2019-0100294 filed on Aug. 16, 2019 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates to a multilayer capacitor and a board having the same mounted thereon.

BACKGROUND

A multilayer capacitor is widely used as an information technology (IT) component of a computer, a personal digital assistant (PDA), a mobile phone, and the like, due to advantages thereof such as small size, high capacitance, and ease of mounting. Also, the multilayer capacitor is widely used as an electrical component due to characteristics thereof such as high reliability and high strength.

With the recent trend for miniaturization and multifunctionalization of electronic devices, a multilayer capacitor is also required to have a small size and high capacitance. To this end, a multilayer capacitor, having a structure in which an internal electrode is exposed in a width direction of a capacitor body to significantly increase an area of the internal electrode in the width direction, has been manufactured.

In a multilayer capacitor having such a structure, a capacitor body is manufactured and side portions are respectively attached to both surfaces of the capacitor body in the width direction during a pre-sintering process, such that the side portions cover exposed portions of the internal electrode.

However, a multilayer capacitor, having such a structure in which side portions are attached after the internal electrode is exposed in a width direction of a capacitor body as described above, may suffer from degradation in moisture resistance reliability and toughness resulting from shrinkage after sintering.

SUMMARY

An aspect of the present disclosure is to provide a multilayer capacitor, capable of increasing capacitance and improving moisture resistance reliability and toughness, and a mounting board of the multilayer capacitor.

According to an aspect of the present disclosure, a multilayer capacitor includes a capacitor body including dielectric layers and first and second internal electrodes, the capacitor body having a first surface and a second surface opposing each other, a third surface and a fourth surface, connected to the first surface and the second surface, opposing each other, and a fifth surface and a sixth surface, connected to the third surface and the fourth surface, opposing each other, the first internal electrode being exposed through the third, fifth, and sixth surfaces, and the second internal electrode being exposed through the fourth, fifth, and sixth surfaces, a first side portion and a second side portion, respectively disposed on the fifth surface and the sixth surface of the capacitor body, and a first external electrode and a second external electrode, respectively connected to the third surface and the fourth surface of the capacitor body to respectively be connected to the first internal electrode and the second internal electrode. The first and second side portions comprise an acicular second phase including a glass comprising aluminum (Al) and silicon (Si), manganese (Mn), and phosphorus (P), and a volume of the second phase is 30% or more with respect to the entire first and second side portions.

A content of Al and Si in the first and second side portions may be twice or more that of Al and Si in the capacitor body.

The dielectric layer may have an average thickness of 0.4 μm or less.

The first and second internal electrodes may have an average thickness of 0.41 μm or less.

The number of the first and second internal electrodes laminated may be 400 or more.

The first and second side portions may have an average thickness of 10 to 20 μm.

The capacitor body may include an active region, in which the first and second internal electrodes overlap each other, and upper and lower cover regions, respectively disposed on upper and lower surfaces of the active region.

Each of the upper and lower cover regions may have a thickness of 20 μm or less.

The first and second external electrodes may have an average thickness of 10 μm or less.

The first and second external electrodes may respectively include first and second connection portions, respectively disposed on the third and fourth surfaces of the capacitor body to respectively be connected to the first and second internal electrodes, and first and second band portions, respectively extending from the first and second connection portions to a portion of the first surface of the capacitor body.

According to another aspect of the present disclosure, a mounting board of a multilayer capacitor includes a substrate, including first and second electrode pads on one surface thereof, and a multilayer capacitor mounted such that first and second external electrodes are respectively connected to the first and second electrode pads.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of the present disclosure will be more clearly understood from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view illustrating a multilayer capacitor according to an embodiment of the present disclosure;

FIG. 2 is a cross-sectional view taken along line I-I′ in FIG. 1;

FIGS. 3A and 3B are plan views illustrating laminated structures of first and second internal electrodes of the multilayer capacitor in FIG. 1, respectively;

FIG. 4 is a cross-sectional view taken along line II-II′ in FIG. 1;

FIG. 5 is a cross-sectional view taken along line III-III′ in FIG. 1;

FIG. 6 is a schematic cross-sectional view of a board on which the multilayer capacitor, illustrated in FIG. 1, is mounted; and

FIG. 7 shows a scanning electron micrograph of a mullite, in particular showing the acicular phase, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described as follows with reference to the attached drawings.

However, the present disclosure may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein.

Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Accordingly, the shapes and dimensions of elements in the drawings may be exaggerated for clarity, and the same reference numerals will be used throughout to designate the same or like elements.

Further, the same reference numerals are used throughout the drawings for the elements having similar functions and activities.

In the specification, unless otherwise specifically indicated, when a certain part “includes” a certain component, it is understood that other components may be further included but are not excluded.

To clearly describe the example embodiments, X, Y, and Z indicated in the drawings are defined to represent a length direction, a width direction, and a thickness direction of a multilayer capacitor, respectively.

Additionally, the Z direction may be used in the same sense as a lamination direction in which the dielectric layers are laminated.

FIG. 1 is a perspective view illustrating a multilayer capacitor according to an embodiment of the present disclosure, FIG. 2 is a cross-sectional view taken along line I-I′ in FIG. 1, FIGS. 3A and 3B are plan views illustrating laminated structures of first and second internal electrodes of the multilayer capacitor in FIG. 1, respectively, FIG. 4 is a cross-sectional view taken along line II-II′ in FIG. 1, and FIG. 5 is a cross-sectional view taken along line III-III′ in FIG. 1.

Hereinafter, a multilayer capacitor according to this embodiment will be described with reference to FIGS. 1 to 5.

Referring to FIGS. 1 to 5, a multilayer capacitor 100 includes a capacitor body 110, first and second side portions 141 and 142, and first and second external electrodes 131 and 132.

The capacitor body 110 is in a sintered state after a plurality of dielectric layers 111 are laminated in a Z direction, and adjacent dielectric layers 111 may be integrated with each other such that boundaries therebetween are not readily apparent without a scanning electron microscope (SEM).

The capacitor body 110 may include a plurality of dielectric layers 111 and first and second internal electrodes 121 and 122, having polarities opposite to each other, alternately disposed in the Z direction with respective dielectric layers 111 interposed therebetween.

The capacitor body 110 may include an active region 114, as a portion contributing to forming capacitance of a capacitor, in which the first and second internal electrodes 121 and 122 are alternately disposed with respective dielectric layers 111 interposed therebetween, and upper and lower cover regions 112 and 113, provided on upper and lower surfaces of the active region 114 in the Z direction, as a margin portion.

In this case, each of the upper and lower cover regions 112 and 113 may have a thickness of 20 μm or less.

A shape of the capacitor body 110 is not limited, but may be substantially hexahedral. The capacitor body 110 may have first and second surfaces 1 and 2 opposing each other in the Z direction, third and fourth surfaces 3 and 4, connected to the first and second surfaces 1 and 2, opposing each other in an X direction, and fifth and sixth surfaces 5 and 6, connected to the first and second surfaces 1 and 2 as well as to the fifth and sixth surfaces 5 and 6, opposing each other. In this embodiment, the first surface 1 may be a mounted surface of the multilayer capacitor 100.

The dielectric layer 111 may include ceramic power particles, for example, BaTiO₃-based ceramic powder particles.

The BaTiO₃ (BT)-based ceramic powder may be (Ba_(1-x)Ca_(x))TiO₃, Ba(Ti_(1-y)Ca_(y))O₃, (Ba_(1-x)Ca_(x)) (Ti_(1-y)Zr_(y))O₃, or Ba(Ti_(1-y)Zr_(y))O₃, prepared by partially employing cesium (Ca), zirconium (Zr), and the like, in BaTiO₃, but the present disclosure is not limited thereto.

A ceramic additive, an organic solvent, a plasticizer, a binder, a dispersant, and the like, may be further added to the dielectric layer 111, together with the ceramic powder particles.

The ceramic additive may include, for example, a transition metal oxide or a transition metal carbide, a rare earth element, magnesium (Mg), aluminum (Al), or the like.

The first and second internal electrodes 121 and 122 are electrodes to which opposite polarities are applied, and may be disposed on respective dielectric layers 111 to be alternately laminated in the Z direction and may be alternately disposed inside the capacitor body in the A direction with a single dielectric layer 111 therebetween.

In this case, the first and second internal electrodes 121 and 122 may be electrically insulated from each other by the dielectric layer 111 disposed therebetween.

The first internal electrode 121 is exposed through the third, fifth, and sixth surfaces 3, 5 and 6 of the dielectric layer 111.

In this case, the first internal electrode 121 may also be exposed through a corner, connecting the third surface 3 and the fifth surface 5 of the capacitor body 110, and a corner connecting the third surface 3 and the sixth surface 6 of the capacitor body 110.

The second internal electrode 122 is exposed through the fourth, fifth, and sixth surfaces 4, 5, and 6 of the dielectric layer 111.

In this case, the second internal electrode 122 may also be exposed through a corner, connecting the fourth surface 4 and the fifth surface 5 of the capacitor body 110, and a corner connecting the fourth surface 4 and the sixth surface 6 of the capacitor body 110.

In this case, end portions of the first and second internal electrodes 121 and 122, alternately exposed through the third and fourth surfaces 3 and 4 of the capacitor body 110, may be connected to the first and second external electrodes 131 and 132 disposed on both end portions of the capacitor body 110 in the X direction to electrically connected thereto, respectively.

According to the above configuration, charges are accumulated between the first and second internal electrodes 121 and 122 when a predetermined voltage is applied to the first and second external electrodes 131 and 132.

In this case, capacitance of the multilayer capacitor 100 is in proportion to an overlapping area of the first and second internal electrodes 121 and 122 overlapping each other in the Z direction in an active region 114.

As in this embodiment, when the first and second internal electrodes 121 and 122 are configured, not only basic areas of the first and second internal electrodes 121 and 122 but also a vertically overlapping area thereof is increased. Therefore, the capacitance of the multilayer capacitor 100 may be increased.

For example, when the area of the overlapping region of the first and second internal electrodes 121 and 122 is significantly increased, capacitance of a capacitor having even the same size may be significantly increased.

In addition, since a step, caused by lamination of internal electrodes, may be reduced to improve accelerated lifespan of insulation resistance, the multilayer capacitor 100 having improved capacitance characteristics and improved reliability may be provided.

In this case, a material of the first and second internal electrodes 121 and 122 is not limited, and the first and second internal electrodes 121 and 122 may be formed using a conductive paste including a precious metal material or at least one of nickel (Ni) and copper (Cu).

The conductive paste may be printed by screen printing, gravure printing, or the like, but a printing method of the conductive paste is not limited thereto.

An average thickness of the first and second internal electrodes 121 and 122 may be determined depending on purposes thereof and may be, for example, 0.41 μm or less.

In addition, the total number of the laminated first and second internal electrodes 121 and 122 may be 400 or more.

Accordingly, the multilayer capacitor 100 according to an example embodiment may be used as a component, requiring a large size and high capacitance, such as an IT component.

The first side portion 141 is disposed on the fifth surface 5 of the capacitor body 110, and the second side portion 142 is disposed on the sixth surface 6 of the capacitor body 110.

The first and second side portions 141 and 142 are in contact with tips of portions, exposed through the fifth and sixth surfaces 5 and 6 of the capacitor body from the first and second internal electrodes 121 and 122, to cover the tips.

The first and second side portions 141 and 142 serve to protect the capacitor body 110 and the first and second internal electrodes 121 and 122 from external impact and the like, and to secure insulation properties and moisture resistance reliability in the vicinity of the capacitor body 110.

The first and second side portions 141 and 142 include an acicular mullite second phase including a glass including aluminum (Al) and silicon (Si), manganese (Mn), and phosphorous (P).

In this case, a volume of the second phase may be 30% or more with respect to the entire first and second side portions 141 and 142.

Aluminum (Al) and silicon (Si) contents of the first and second side portions 141 and 142 may be twice or more than those of the capacitor body 110.

Alumina content of the first and second side portions 141 and 142 is high, and the first and second side portions 141 and 142 may be densified by a low melting point material. As the amount of generated mullite secondary phases is increased, strength of the first and second side portions 141 and 142 may be proportionally increased.

Such a mullite second phase of this embodiment may be physically crosslinked to an adjacent mullite second phase to be physically linked thereto.

Accordingly, the first and second side parts 141 and 142 may have better resistance against external physical impact and may block a moisture penetration path into the capacitor body 110.

In addition, the second phase of the present disclosure may improve grain density of the first and second side portions 141 and 142 depending on a chemical low-temperature sintering action.

Accordingly, the first and second side parts 141 and 142 may have better resistance against external physical impact, and the water penetration path of the ceramic body 110 may be blocked.

The mullite second phase of this embodiment may improve the moisture resistance reliability and hardness of the capacitor body 110 relatively more than other second phases, for example, a phosphate-based second phase.

The average thickness of the first and second side portions 141 and 142 in the Y direction may be 10 to 20 μm.

When the average thickness of the first and second side portions 141 and 142 in the Y direction is low, a ratio of the capacitor body 110 in a multilayer capacitor of the same standard may be increased. Thus, the capacitance of the multilayer capacitor 100 may also be increased.

In general, when an average thickness of the side portion is low, the moisture resistance reliability and toughness of the side portion may be degraded. However, the multilayer capacitor 100 according to this embodiment may include the first and second side portions 141 and 142, including the second phase, to prevent degradations in reliability and toughness of the multilayer capacitor 100, even when the average thickness of the first and second side portions 141 and 142 is low.

As in the present embodiment, when the average thickness of the first and second side portions 141 and 142 in the Y direction is 10 to 20 μm, an effect of preventing degradations in capacitance, reliability, and toughness may be optimized.

Each of the first and second side portions 141 and 142 may have an acicular shape with a major axis and a minor axis.

A phosphate-based glass according to a related art forms an acicular second phase after sintering. An example of the structure of an acicular second phase is shown FIG. 7 which shows a scanning electron micrograph (SEM) of a mullite in accordance with an embodiment of the present disclosure. A second phase having a mullite composition according to this embodiment may have an acicular shape and may have a major axis having a larger size and a higher thickness than a major axis of a phosphate-based second phase including only a common P component. Thus, the moisture resistance and the hardness of the first and second side parts 141 and 142 may be further improved.

The first and second external electrodes 131 and 132 may be provided with voltages of polarities opposite to each other, and may be disposed on both end portions of the body 110 in the X direction. The first and second external electrodes 131 and 132 may be connected to portions exposed through the third and fourth surfaces 3 and 4 of the capacitor body 110 to be electrically connected thereto, respectively.

In this case, the first and second external electrodes 131 and 132 may have an average thickness of 10 μm or less.

Accordingly, the multilayer capacitor 100 may be miniaturized, and the manufacturing costs of the multilayer capacitor 100 may be reduced.

When the thickness of each of the first and second external electrodes 131 and 132 is low, the moisture resistance reliability and the hardness of the capacitor body 110 may be generally degraded. However, in this embodiment, the first and second side portions 141 and 142 include an acicular mullite second phase including a glass including Al and Si, Mn, and P to prevent degradation in moisture resistance reliability and hardness even if each of the first and second external electrodes 131 and 132 has a thickness of 10 μm or less. As a result, miniaturization and reduced manufacturing costs of the multilayer capacitor 100 may be expected.

The first external electrode 131 may include a first connection portion 131 a and a first band portion 131 b.

The first connection portion 131 a is disposed on the third surface 3 of the capacitor body 110 and is in contact with an end portion, exposed outwardly of the first internal electrode 121 through the third surface 3 of the capacitor body 110, to connect the first internal electrode 121 and the first external electrode 131 to each other.

The first band portion 131 b is a portion extending from the first connection portion 131 a to a portion of the first surface 1 of the capacitor body 110.

As necessary, in order to improve adhesive strength and the like, the first band portion 131 b may further extend to the second, fifth, and sixth surfaces 2, 5, and 6 of the capacitor body 110 to cover one end portion of the side portions 141 and 142.

The second external electrode 132 may include a second connection portion 132 a and a second band portion 132 b.

The second connection portion 132 a is disposed on the fourth surface 4 of the capacitor body 110 and is in contact with an end portion, exposed outwardly of the second internal electrode 122 through the fourth surface 4 of the capacitor body 110, to connect the second internal electrode 122 and the second external electrode 132 to each other.

Each of the first and second external electrodes 131 and 132 may include a plating layer for at least a portion thereof to improve structural reliability, ease of board mounting, durability to the outside, heat resistance, and equivalent series resistance (ESR).

For example, the plating layer may be formed by sputtering or electric deposition, but a method of forming the plating layer is not limited thereto.

The plating layer may include a largest amount of nickel, but is not limited thereto. The plating layer may be implemented using copper (Cu), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), lead (Pb) alone, or alloys including at least one thereof.

According to this embodiment, the first and second side portions 141 and 142 may include an acicular mullite second phase including a glass containing aluminum (Al) and (Si), manganese (Mn), and phosphorus (P) in an amount of 30% or more with respect to the entire first and second side portions 141 and 142. Thus, the first and second side portions 141 and 142 may increase strength of the first and second side portions 141 and 142 by 30% as compared to a side portions, not including the secondary phase.

In the case of a multilayer capacitor including a side portion according to a related art, cracking resistance of the side portion is low. Thus, cracking occurs in the side portion and moisture penetrates into the cracking to degrade reliability of the multilayer capacitor.

In this embodiment, cracking resistance of the first and second side portions 141 and 142 may be increased to improve the moisture resistance reliability of the multilayer capacitor 100.

In this embodiment, the dielectric layer 111 may have an average thickness of 0.4 μm or less.

Since the thickness of the dielectric layer 111 corresponds to a distance between the first and second internal electrodes 121 and 122, the capacitance of the multilayer capacitor 100 may be improved when the thickness of the dielectric layer 111 is low.

The first and second internal electrodes 121 and 122 may have an average thickness of be 0.41 μm or less.

Since the multilayer capacitor 100 of this embodiment has a structure in which the first and second internal electrodes 121 and 122 are exposed through the fifth and sixth surfaces 5 and 6 of the capacitor body 110, a step with respect to the capacitor body 110 may be reduced on end portions of the first and second internal electrodes 121 and 122 in the Y direction.

Accordingly, even when the thickness of the dielectric layer 111 and the first and second internal electrodes 121 and 122 is reduced as described above to achieve multilayer thinning, there is no significant problem with the reliability of the multilayer capacitor 100. Therefore, the reliability may also be secured while increasing the capacity of the capacitor 100.

In addition, when the average thickness of the first and second internal electrodes 121 and 122 is reduced as described above, shrinkage after sintering may be decreased. Therefore, a diameter of a void in the end portion of the capacitor body 110 may be further reduced to further improve the reliability of the multilayer capacitor 100.

Referring to FIG. 6, a mounting board of a multilayer capacitor according to this embodiment may include a substrate 210, including first and second electrode pads 221 and 222 on one surface thereof, and a multilayer capacitor 100 mounted such that first and second external electrodes 131 and 141 are respectively connected to the first and second electrode pads 221 and 222 on an upper surface of the substrate 210.

In this embodiment, the multilayer capacitor 100 is illustrated and described as being mounted on the substrate 210 by solders 231 and 232 but, as necessary, a conductive paste may be used rather than a solder.

As described above, an internal electrode may be exposed in a width direction of a capacitor body to increase capacitance of a multilayer capacitor, and a side portion may include an acicular mullite second phase including a glass including Al and Si, Mn, and P in an amount of 30% or more with respect to the entire side portion to improve moisture resistance reliability and toughness of the multilayer capacitor depending on a physical crosslinking action and a chemical low-temperature sintering action of the second phase of the side portion.

While embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present disclosure as defined by the appended claims. 

What is claimed is:
 1. A multilayer capacitor comprising: a capacitor body including dielectric layers and first and second internal electrodes, the capacitor body having a first surface and a second surface opposing each other, a third surface and a fourth surface, connected to the first surface and the second surface, opposing each other, and a fifth surface and a sixth surface, connected to the third surface and the fourth surface, opposing each other, the first internal electrode being in contact with the third, fifth, and sixth surfaces, and the second internal electrode being in contact with the fourth, fifth, and sixth surfaces; a first side portion and a second side portion, respectively disposed on the fifth surface and the sixth surface of the capacitor body, and comprising an acicular second phase including manganese (Mn), and phosphorus (P), and a glass comprising aluminum (Al) and silicon (Si), wherein a volume of the second phase is 30% or more with respect to an entirety of the first and second side portions; and a first external electrode and a second external electrode, respectively connected to the third surface and the fourth surface of the capacitor body to respectively be connected to the first internal electrode and the second internal electrode.
 2. The multilayer capacitor of claim 1, wherein a content of Al and Si in the first and second side portions is twice or more that of Al and Si in the capacitor body.
 3. The multilayer capacitor of claim 1, wherein the dielectric layer has an average thickness of 0.4 μm or less.
 4. The multilayer capacitor of claim 1, wherein the first and second internal electrodes have an average thickness of 0.41 μm or less.
 5. The multilayer capacitor of claim 1, wherein the number of the first and second internal electrodes laminated is 400 or more.
 6. The multilayer capacitor of claim 1, wherein the first and second side portions have an average thickness in a range from 10 to 20 μm.
 7. The multilayer capacitor of claim 1, wherein the capacitor body comprises an active region, in which the first and second internal electrodes overlap each other, and upper and lower cover regions, respectively disposed on upper and lower surfaces of the active region.
 8. The multilayer capacitor of claim 7, wherein each of the upper and lower cover regions has a thickness of 20 μm or less.
 9. The multilayer capacitor of claim 1, wherein the first and second external electrodes have an average thickness of 10 μm or less.
 10. The multilayer capacitor of claim 1, wherein the first and second external electrodes respectively comprise: first and second connection portions, respectively disposed on the third and fourth surfaces of the capacitor body to respectively be connected to the first and second internal electrodes; and first and second band portions, respectively extending from the first and second connection portions to a portion of the first surface of the capacitor body.
 11. A mounting board of a multilayer capacitor, comprising: a substrate comprising first and second electrode pads on one surface thereof; and the multilayer capacitor of claim 1 disposed on the substrate such that first and second external electrodes are respectively connected to the first and second electrode pads.
 12. A multilayer capacitor comprising: first internal electrodes being in contact with a first end surface and a pair of side surfaces of a capacitor body; second internal electrodes being in contact with a second end surface and the pair of side surfaces of the capacitor body, a portion of the second internal electrodes overlapping a portion of the first internal electrodes; dielectric layers interposed between adjacent first and second internal electrodes; side portions disposed on the pair of side surfaces and comprising a crosslinked acicular second phase including a glass comprising aluminum (Al), silicon (Si), manganese (Mn), and phosphorus (P); a first external electrode disposed on the first end surface and connected to the first internal electrodes; and a second external electrode disposed on the second end surface and connected to the second internal electrodes, wherein the second phase constitutes at least 30% by volume of the side portions.
 13. The multilayer capacitor of claim 12, wherein the second phase comprises a mullite. 